The invention relates to a device for connecting a tool to a mechanical rotary drive. The tool can e.g. be a bit or also drilling/cutting tools such as e.g. countersinking cutters, taps or reamers. With tools of this type the problem arises that the alignment between the workpiece to be rotated, e.g. a screw, and tool is not always correct. Numerous proposals for solving this problem exist.
For example a flexible socket wrench is known (DE 36 24 686), where the pivotability is ensured by pins at right angles to the longitudinal axis of the tool.
A screwdriver with an articulated head part is also known (DE 94 03 845), where use is made of a tubular rubber spring.
A device for connecting screwdriver inserts to a drive mechanism is known (DE 41 43 218), where a torsion coupling is provided, which allows an angular movement between the driving part and the driven part.
In the case of socket wrenches a further problem arises in that very high torques can occur on stopping the screwing movement and which can lead to the destruction of the tool or also the screw. If on turning a screw into hard wood the screw head reaches the wood surface, a sudden torque occurs and a release clutch on the drive is no longer able to immediately flatten the torque peaks.
The problem of the invention is to provide a device for connecting a tool to a mechanical rotary drive, which compared with the prior art offers advantages with respect to the service life of the tool and/or screw.
The invention relates to a device for connecting a tool to a rotary driving apparatus through a spring disc coupling, also referred to herein as a spring washer coupling.
The spring washer coupling or clutch is a component built up in one piece from a plurality of parallel, ring-shaped washers, which are interconnected with the aid of webs. The webs pass along a diameter. The webs between two washers are displaced by 90xc3x8 with respect to the webs between the next two washers. Such a spring washer coupling is e.g. known from EP 318 669 and is intended to compensate any alignment errors of the axes which occur and these can be both angle errors and displacement errors.
According to a further development of the invention the drive element and driven element are mounted in such a way that they are always positioned coaxially. In this case the spring washer coupling is not used for compensating alignment errors of rotation axes. Instead it serves exclusively to bring about in the rotation direction a slight flexibility or resilience of the coupling element and to reduce the aforementioned impacts when the screwing movement is suddenly stopped.
However, it is also possible to mount the drive element and driven element in such a way that an angle compensation of their rotation axes is possible.
In order to bring the coupling element in a particularly simple manner into rotary engagement with the drive element and/or driven element, according to the invention it is possible for the at least one entry end of the coupling element to have a polygonal, e.g. hexagonal shape, which engages in a complimentary recess of the drive element and/or driven element.
The spring washer coupling also has resilience characteristics in the axial direction. According to the invention the coupling element can have an end clearance.
A possible tool, which can be connected to the rotary drive by the device is a bit for a mechanical screwdriver. Here it is mainly a question of reducing sudden torque peaks.
However, according to the invention the device can also be used with a drill, where it is appropriate to integrate the described coupling element e.g. into a drill chuck.
According to a further development of the invention the coupling element is constructed in one piece with the drive element and the driven element. As a result the number of components of the connecting element is reduced. In addition, the device then has a simpler construction.
According to a further development of the invention the gaps between the parallel, ring-shaped washers of the spring washer coupling are filled, e.g. extruded completely or partly with a relatively hard or rigid elastomer material. Extrusion with a soft elastomer material does not modify the resilience characteristics of the spring washer coupling, but can prevent the penetration of dirt. Extrusion can take place in such a way that also the outside is covered with an elastomer coating, so that it is no longer possible to see the slits.